The present invention relates generally to a bearing mechanism, a carriage assembly having a head arm mounted on a bearing mechanism, and a magnetic disk drive mounted with a carriage assembly, and more particularly, to a structure of a bearing mechanism.
A magnetic disk drive includes a spindle motor portion, a carriage portion, an actuator portion, and a base and cover portion. The spindle motor portion includes a magnetic disk secured onto a spindle hub by means of a disk clamp. The carriage portion includes a pivot bearing for rotatably moving a magnetic head, which is supported by a suspension mounted on a head arm, to any desired position on the magnetic disk. The actuator portion includes a magnetic circuit for driving the carriage portion. The base and cover portion accommodates all of the aforementioned portions.
The pivot bearing forming part of the carriage portion must be capable of instantaneously and accurately rotating the magnetic head performing reading and writing operations to any given location on the magnetic disk. An extremely high rotational accuracy is therefore required of the pivot bearing. A high bearing stiffness is also required of the pivot bearing for the following reason. Specifically, if a natural frequency of the carriage is low, the carriage resonates during operation, thus becoming unable to accurately position the magnetic head. For these reasons, preloads in an axial direction and a radial direction are applied to a ball bearing forming the pivot bearing.
The conventional pivot bearing uses two ball bearings to provide a structure having preloads contained internally as described in Patent Document 1 (Japanese Patent Laid-open No. 2003-77237).